Are the x and y peak values from matlab's norm2xcorr located in the middle of the object ?

I want to use a cross correlation program to detect the movement of a particle that is trapped, the movement of the particle is barely noticeable. I want to use a cross correlation program to detect the movement of the particle which has been captured across multiple frames. My question now is how do I detect these displacements? I know that that using the cross correlation you get x and y pecks, I was going to subtract the x and y peaks from the radius of the particle to get the offsets of the particle but I don't know if the x and y peak values are located in the middle of the particle. Also how do I obtain the radius of the particle?